A battery module includes cylindrical battery cells, a module housing, and a bus bar. The bus bar includes a main body portion that is positioned at a top or a bottom of the plurality of cylindrical battery cells and has a plate shape having upper and lower surfaces that are broader than a lateral surface of the main body portion in a horizontal direction; and a contact portion that is configured to electrically contact and be connected to an electrode terminal formed in one of the plurality of cylindrical battery cells, extends and protrudes from the main body portion in a horizontal direction, is stepped from the main body portion in a direction toward where the electrode terminal is positioned, and includes a branched structure bifurcated in two directions with respect to a direction in which the contact portion extends and protrudes from the main body portion.